An aspect of the present invention relates to an intelligent ultrasonic system and a control method thereof, and more particularly, to an intelligent ultrasonic system which can reset a parameter of an ultrasonic sensor mounted on a vehicle in response to a surrounding environment, and a control method thereof. Another aspect of the present invention relates to a rear collision warning apparatus for a vehicle and a control method thereof, and more particularly, to a rear collision warning apparatus for a vehicle, which can not only calculate a collision risk index, but also generate a prefill braking pressure to prepare for emergency braking, based on weights for a plurality of sensors for sensing the rear of the vehicle and risk indexes of the plurality of sensors which sensed an obstacle, and a control method thereof.
In general, a front/back warning system for a vehicle refers to a system that generates a warning according to a result obtained by measuring a distance to an object at the front or back of the vehicle using an ultrasonic sensor as illustrated in FIG. 1, in order to prevent a collision accident between the object and the vehicle during parking or stopping.
At this time, the front/back warning system uses the ultrasonic sensor as a sensor for sensing a forward/backward object. In order to normally sense a forward/backward object from a signal sensed through the ultrasonic sensor, the front/back warning system must perform an initialization operation when the vehicle is started. The initialization operation (or initialization operation of the ultrasonic sensor) is an operation to set a kind of reference value (or parameter) for sensing only a signal reflected from the object while excluding a noise signal.
Such an initialization operation (initialization operation of the ultrasonic sensor) has been performed to correct differences in sensitivity among a plurality of ultrasonic sensors. However, the initialization operation may not correct a change in the overall sensing performance of the plurality of ultrasonic sensors depending on the surrounding environment (climate, humidity or weather).
Since at least several feedback processes are repeated during the initialization operation (or the initialization operation of the ultrasonic sensor), a considerable amount of time may be required until the sensing function of the ultrasonic system is normalized.
In general, various recognition methods are applied in order to recognize an obstacle around a vehicle. The various recognition methods may include a motion estimation method, a thing recognition method, a heterogeneous sensor fusion method and a method based on a cross region among cameras (hereafter, referred to as a cross region-based method).
The motion estimation method applies a complex motion estimation technique such as an optical flow, using the existing image processing technique, the existing monitoring cameras and the existing object tracking technique.
The thing recognition method recognizes a thing using an advanced learning technique such as pattern recognition.
The heterogeneous sensor fusion method recognizes a thing by fusing a detection result of a camera which serves to detect a moving object and a detection result of a radar, laser scanner or ultrasonic sensor which serves to detect a stationary obstacle.
The cross region-based method recognizes a thing from an image obtained by combining cross regions of images taken through a plurality of cameras at the same point of time.
As such, there are a variety of warning systems which detect an obstacle therearound through various methods, and not only warn a driver about the presence of the obstacle, but also determine a collision risk and warn the driver about the collision risk.
However, when an obstacle is detected through various methods, the detection reliability may differ depending on the methods or differ depending on the surrounding environments. Therefore, since the detection reliability may be degraded depending on a selected method, the reliability of the collision warning process may also be degraded.
The related arts of the present invention are disclosed in Korean Patent Publication No. 10-2001-0016962 published on Mar. 5, 2001 and entitled “Back warning method with sensor initialization function”, and Korean Patent Registration No. 1734490 published on May 11, 2017 and entitled “AVM system using ultrasonic sensor and control method thereof”.